A Red Giant’s Death Throes

This article is about how an international team of astronomers were able to use the ALMA Telescope in Northern Chile to observe the final acts the Red Giant star LL Pegasi and its companion star 3,400 light years away from Earth. The star is currently shedding its gases in a strong outflowing wind which gives the star a beautiful spiral pattern made of the gases. According to the astronomers, the orbital motion of the mass-losing star is causing its gases to spin out of it like sprays of water from a garden sprinkler. Through observations it was determined that the stars highly elliptical orbit is why the gases are behaving the way they are. The data collected is said to be able to help astronomers understand more about the orbits of these types of stars and how they evolve when the stars lose most of their mass.

This connects to the conceptual objective of “I can describe how stars evolve and die” because it is about a star dying. To connect the article further I will explain a little about a stars evolution and death. LL Pegasi is a Red Giant so that means that it is a Low-Mass star. Before LL Pegasi became a Red Giant it was a main sequence star. Hydrogen fusion supplies thermal energy that keeps a main sequence star in balance. When the core to the stars hydrogen was depleted, nuclear fusion stopped. With no nuclear fusion the star could not stop the inward pull of gravity and the core shrank. While this happened the outer layers of the star expanded into it becoming a Red Giant, a process that probably took about a billion years. After existing in this state for about 100 million years the Red Giant will start to die. The cores helium will run out and fusion will stop. Now the core will start to shrink again under the weight of gravity and the star will swell in size again. With the carbon core of the star unable to undergo fusion and provide energy to the star the star will finally die. The luminosity and radius of the dying star will keep growing and produce more wind. The star will then eject its outer layers into space which will create a huge gas cloud that will fly away from the carbon core. The carbon core will still be very hot as it turns into a planetary nebula. After about 100,000 years the nebula will fade as a White Dwarf is left behind.

This article was interesting because it included a picture and two videos in it which helped to visualize what is happening to LL Pegasi. I’m surprised that the ALMA telescope was able to get as detailed of images as it got. I thought that most long range photos from telescopes were pretty underwhelming when you got outside of our solar system. Hopefully the data that was gathered on this star will help astronomers discover more about other stars around the galaxy. From the amount of articles I’ve been reading on subjects like these it seems like any new information, no matter how small, helps.